Which of the following hormones is critical for reproductive function in both males and females?

Follicle-stimulating hormone (FSH) plays a crucial role in reproductive function for both males and females. In females, FSH is essential for the development and maturation of ovarian follicles, which are necessary for ovulation and the overall regulation of the menstrual cycle. In males, FSH is involved in the regulation of spermatogenesis, the process of sperm production in the testes. By promoting the growth and function of Sertoli cells, FSH supports the maturation of sperm cells.

This dual role in both male and female reproductive systems underscores its importance as a key hormone in endocrine regulation of reproduction. The other hormones listed have specific roles that are not as universally critical for reproductive functions across genders. For example, growth hormone primarily influences growth and metabolism, thyroid-stimulating hormone regulates thyroid function and metabolism, while prolactin is primarily involved in lactation and has a more limited role in reproductive health specifically related to milk production.